1. Field of the Invention
The present invention relates to a locking structure, and in particular to a preload biased structure of a linear rail for locking a sliding block tightly in advance.
2. Description of Related Art
Precision industry has become one of the foundations of the modern high-tech culture. Precision industry is part of various traditional industries, such as photo-electronics, semiconductor, timepiece, mold, nanotechnology and etc.
In the field of precision industry, linear transmission elements and their associated products are widely used to many aspects, such as linear rails and ball screws. Especially, the linear rails have been widely mounted on many large-sized precision machines and equipment, thereby increasing the precision, smoothness, stability and lifetime of the parts of the machine.
Specifically speaking, the linear rail becomes more and more important and even indispensable. The linear rail is used to generate a precise linear displacement, thereby allowing a machine to perform a transmission, machining or positioning action with high precision. The linear rail refers to a combination of a rail and a sliding block movable linearly on the rail. The sliding block is constituted of a plurality of precision elements. The sliding block is used to support an object that is to move linearly thereon.
Since the linear rail is applied to a high-precision process, the acceptable error is very small. A minor defect in the linear rail may cause a serious problem, and in turn the manufacturer may suffer great losses. Please refer to FIG. 1, which shows a conventional linear rail. The conventional linear rail comprises a rail 1a and a sliding block 2a. The sliding block 2a is slidably disposed on the rail 1a. The sliding block 2a is constituted of a sliding element 21a, a supporting element 22a and two connecting pieces 23a provided on the front and rear end of the sliding base 21a. The above three members are slidably disposed on the rail 1a. The above members constitute a linear rail, whereby the sliding block 2a can generate an expected linear displacement on the rail 1a. 
However, in practice, the conventional linear rail has some problems as follows.
(I) In assembling, the supporting element 22a and the sliding base 21a cannot be fixed to each other tightly in advance. Therefore, vibrations or collision generated in assembling may cause the supporting element 22a to loosen and fall off the sliding base 21a. 
(II) When the sliding block 2a generates a reciprocating movement on the rail 1a, a force may be generated in longitudinal direction (i.e., the moving direction). Thus, the connecting pieces 23a at the front and rear end of the sliding rail 2a may be subjected to a compression force or a tensile force. These forces will cause the constituent elements in the sliding block 2a to vibrate due to tiny gaps between these constituent elements, so that noise and excessive wear will occur. Even damage may occur to the linear rail. Because of the above limitation resulting from the technical design of the prior art, the inventor strives via real world experience and academic research to develop the present invention, which can effectively improve the limitations described above.